While pulverized coal is chiefly composed of carbon particles, it also contains as impurites particulate ash such as particles of SiO.sub.2, CaO, Al.sub.2 O.sub.3, etc. When put into use as fuel, pulverized coal should advantageously contain no or at least reduced ash. A conventional method heretofore employed to purify pulverized coal comprises adding pulverized coal to water followed by stirring, and subsequently adding to the mixture oil as a separating agent again followed by agitating. Ash can be separated and removed from the coal by utilizing the lipophilic property of coal. With such a method, however, not only is the working efficiency low but also is it difficult to control separation accuracy.